Enhancing Energy Quality in a Breeze Yard Using SMEs - Research Paper Example

IMPROVING WIND POWER QUALITY USING SMES By Student’s name Course code and name Professor’s name University name City, State Date of submission Abstract The increased use of renewable energy has yielded to a focus in the techniques aimed at improvement and stabilization of output. Wind energy to be more specific is faced by serious fluctuations in voltages and frequencies among other issues that are highlighted herein. Therefore there is need to pursue the topic of wind power improvement and stabilisation further so as to establish better means of achieving desirable characteristics at the consumer end. In way of research it is pointed out that an upcoming technology called superconducting magnetic energy storage (SMES) is fast becoming a very important tool for stabilization and improvement of power quality due to the active nature of power compensation it possesses. This thesis through succinctly crafted objectives looks into the viability issue of SMES for application in the wind energy sector. As such, these research objectives are identified as; a bid to demonstrate how SMES can be utilised in resolving the power instability issues associated with voltage fluctuation, to demonstrate how SMES can be deployed in solving the power instability issues related to frequency fluctuations and lastly to demonstrate how wind power quality can be enhanced using flexible AC transmission systems (FACTS) approach available in SMES. All these objectives are to be fulfilled through a simulation methodology called MATLAB/ SIMULINK software. The SMES are supposed to approach the problems at hand through power compensation and later on release and refine the energy through inbuilt mechanisms. Researches carried out prior to the simulation exercise indicate that the SMES can be utilised for reactive and active power compensation thereby resulting to a smooth output voltage. The interest of this research shall therefore improve the vision set by the energy departments around the world and the global warming issue by creating clean alternative energy. Table of Contents Abstract 2 Table of Contents 4 1 Introduction 5 1.1 Background to Study 5 1.2 A Brief History of Electrical Energy Storage 7 1.3 Objectives of Study 9 1.4 Rationale of Study 10 2 Literature Review 12 2.1 Wind Energy 12 2.1.1 Overview of Wind Energy 12 2.1.2 Dynamics of Wind Energy 14 2.2 Superconducting Magnetic Energy Storage 16 2.2.1 Operating Principles of SMES 16 2.2.2 Application of SMES in Wind Energy Improvement 18 3 Research Methodology 22 3.1 Modelling for Objective 1 23 3.2 Modelling for Objective 2 24 3.3 Modelling for Objective 3 25 4 References 27 5 Appendix 29 5.1 SMES Controller Model 29 1 Introduction 1.1 Background to Study The increased demand for steady electrical power in industries and homes has led to innovation of new power generation and transmission systems. While quality of power and equipment safety is an issue of concern to the entire consumer base, little has been done to ensure that the end user is getting the value paid for. As such, increased researches have emerged to cater for the power stabilization as an approach to enhance power quality. It is also to be noted that because of climatic changes as a result of global warming, pacts seeking to commercialize the low quality energy sources (renewable energy) are on an increase as a form of mitigation measure. However, no single renewable energy prides itself as the sole solution to the prominent energy problems that present themselves to humanity. It is then obvious that multiple energy resources have been combined in order to ensure sustainability. Among the upcoming renewable energy sources include solar energy (PV), tidal energy, wave energy and wind energy. The major issues with these sources especially wind energy is that as much as they possess an abundant potential, the possibility of controlling the power output may pose difficulties. This translates to dependency on other sources that are linked together to the grid in order to rid of these variations. These variations are also linked to the fluctuating nature of the driving force in the instance of wind power and wave energy. Prior to loading to the grid, it is therefore required that this form of energy be stabilized in order to avoid fluctuations as is for raw energy. Energy storage is a new concept that is growing very fast and it poses transformation to the renewable energy sources industry. Among the storage technologies considered as the most conducive for utility-scale context include fly wheels, pumped hydro-energy, batteries, conventional capacitors, fuel cell, superconducting magnetic energy storage technology and ultra-capacitors. Due to the nature of disturbances occurring on these sources, superconducting magnetic energy storage SMES has been proposed as the suitable solution to this problem. SMES are considered because of their fast reaction time and high power output. If this technology were to be compared to other existing technologies that aim for the same kind of energy storage, the SMES are highly rated due to their energy release capabilities of up to 10MW per second. Figure 1: SMEs applications in stabilizing energy (Joint Implementation Network, 2014). The comparison table is shown in figure 2 below for further scrutiny. Another important point to be noted with regard to SMES is that their superconducting coils are extremely resistant to any current flows in such situations whereby the cooling process is well achieved. This concept ensures that magnetic energy circulates without any indefinite losses being observed from time to time. Another characteristic of this important system is that comparing to other energy storage systems it is totally discharged with no effect apparently when it is not in use. The lifecycle associated with SMES as compared to its counterparts is higher and is only affected by the energy discharge rate. They can also be installed in remote areas such as substations where complex technologies such as pumped hydro-energy or compressed air are difficult to install (Chen, et al., 2006). Figure 2: Power output comparison for various energy storage systems (Nielsen, 2010). 1.2 A Brief History of Electrical Energy Storage The need for energy storage dates back to the early 20th century when man became more innovative and felt the need of having portable electronics. According to Whittingham (2012), power interruptions also steered this important revolution due to the associated losses. In order to remain relevant in the competitive markets, the industry operators came up with technologies such as flywheels and ultracapacitors to ameliorate the extreme losses that they encountered. Essentially design of power backups took the nature of nickel carbide faribanks that would produce up to a maximum of 40MW. In the late 20th century, a renewed interest in energy storage systems was sparked owing to the emergence of renewable energy sources. Further on, the discovery of electricity driven cars such as the Toyota Prius required an energy capturing system that would save the deteriorating ozone from further depletion. While this may seem as a humble beginning for the energy storage systems, energy storage in wind energy emanated from these developments. The standards that are set by statutory bodies with regard to energy stabilization have continued to rasing their respective bars making it difficult for new entrants to compete effectively when it comes to renewable energy sources. The varying nature of such energy sources has led to innovation of energy storage systems such as hydro-energy storage which was first ustilised in 1909. This systems had an ability of producing 1MW of power after which a relplacement was invented at Blenheim-Gilboa to generate 1.1GW. Renewable energy of low quality would be used to pump water to the reservoir level and would then be utiliused during the power outages thereby achieving an energy convcersion efficiency level of 70%. This development gave birth to the largest energy reservoir based at Raccoon Mountain under the ownership of Tennessee Value Authority (TVA). Developments in the mid 1950s to late 1970s have seen the upcoming of other technologies such as flywheels whose technology was tested for applications of up to 20MW. During the same era, the compressed air energy storage system (CAES) was developed giving rise to a wider choice for energy storage systems. Wind power generated during the onpeak hours would be delivered from the CAES systems during the offpeak hours (Denholm, Ela, Kirby, & Milligan, 2010). Due to load levelling problems, the industry practitioners were forced to venture deep into batteries and capacitor systems in order to establish practicable systems that would enable this kind of action. Fuel cells were a brain child of problems faced from utilization of former energy storage technologies. Electrochemical energy emanating batteries was thought to be more effective athough the commercial viability of this technology failed it terribly as huge loads would more often require expedited chemical reactions in order to sail through (Beguin & Frackowiak, 2009). The advent of superconducting magnetic energy storage technology in 1970s presented more opportuinites in the renewable energy sector. The stabilization procfess and load frequency control that are presented by this technology are reliable and high quality as highlighted in the problem background above. The SMES are more likely to eliminate the problems posed by the low stability wind power and eventually deal with the energy deficits that face cities around the world (Salih, 2012). This paper is mainly concerned with the use of SMES in accelerating the opportunities presented by wind energy. This shall topic shall be approached through MATLAB Simulink simulations meant to indicate the nature of power transformation through the SMES. Both current and previous studies undertaken with regard to wind energy stabilization and SMES are deeply analysed within the literature review section in order to highlight the problems that shall be addressed by this important technology. 1.3 Objectives of Study As this research aims at looking into means of improving and stabilizing power output resulting from wind energy which is a form of renewable energy, the systems designed for this kind of exercise have been factored. The use of SMES in achieving these objectives is in the centre of study and not much consideration has been given to the quantitative nature of the output. The qualitative properties of wind energy which include disturbance, voltage drop and fluctuations, frequency variations and load/ power supply changes shall be addresses by this proposal in a succinct manner that looks at increasing the productivity within the industry. Although there may be other issues arising from the revolutionary approach under which the engineering cadre operates, there shall be significant improvements that shall be imparted as a result of this research. The research objectives are identified as follows: 1. To demonstrate how SMES can be utilised in resolving the power instability issues associated with voltage fluctuation. 2. To demonstrate how SMES can be deployed in solving the power instability issues related to frequency fluctuations. 3. To demonstrate how wind power quality can be enhanced using flexible AC transmission systems (FACTS) approach available in SMES. 1.4 Rationale of Study The proposed study seeks to demystify the importance that SMES technology poses on renewable energy with a propensity towards wind energy. This shall ensure that investors protect consumers against the power surges/ instabilities that are currently a hot topic. Power quality as it emerges should be upgraded owing to the invention of equipment that is power specification sensitive. A slight change in power specification is prone to damage equipment thus it is important that this research looks into the possibilities of deploying the SMES technology in regulating power for consumption purposes. The results obtained from this research shall be used to suggest means of improving power quality by use of SMES. The last objective that shall be achieved by this report is the ability to propose the power stabilization system through an analytical approach utilized in the research methodology. 2 Literature Review This section shall highlight the recent developments that have taken place in the renewable energy industry with particular interest to wind energy. The advantages that SMES’ utilization poses to the industry shall also be discussed in depth in order to quantitatively indicate how they aid in making the output more stable and reliable. According to Baggini (2008), the possibilities possessed by these systems were forecast during the rollout of this technology in 1970s. This concept did not however seem viable at that time though with advancements in technology, the impossibilities have been turned into possibilities. Power systems facing significant issues have therefore been imposed against this solution as a major approach towards eliminating associated problems. It is notable for example how SMES have been utilised in rectifying unstable voltages with high frequency load changes and disturbances especially in renewable energy (Pahlavani , 2011). 2.1 Wind Energy 2.1.1 Overview of Wind Energy The evolution of wind energy dates back to 5000 B.C. when Persian history when the peasants occupying the banks of River Nile harnessed wind power from windmills for use in pumping of water and grinding of cereals. Fast to 1000 A.D. wind power spread across various nations in Europe with the leading example as Netherlands which used windmills to drain lakes for purposes of occupancy. The development of the Halladay windmill under the watch of Daniel Halladay is certainly an achievement that transformed the landscape of West America. In the late 1800s it was observed that farmers had embraced the wind power technology to save themselves from water shortages and also to generate small scale electricity for domestic consumption (Office of Energy Efficiency & Renewable Energy, 2014). The introduction of steel blades in 1890s enhanced the growth of wind power sector due to increased efficiency. According to Office of Energy Efficiency & Renewable Energy (2014), this development led to the erection of over six million windmills in America alone. Wind turbines were eventually designed in Denmark to replace windmills which were now quickly fading from the geography of this country. Due to the difficulties faced during the world war which erupted in 1940s, the introduction of a 1.25MW wind turbine operating on Vermont hilltop became the largest achievement which ended up supplying the local grid. The sky rocketing prices of oil in 1970s saw an increase in word wide migration to renewable with wind being the major beneficiary. Following climate changes, renewable energy has become a handy solution that according to Runyon (2014), has propelled the current installed wind power to 318GW. The resulting wind power has however resulted to many shortcomings with the major one being how to maintain an acceptable level of voltage. The second problem is how to meet the power demand from the interlinked wind power systems. The integration of wind power to the grid is hindered by the instability of such systems which eventually lead to fluctuations of the output at the consumer end. The high penetration of wind power due to high publicity has therefore led flexibility to sources that are fed to the grid thus enhancing the problem of instability and unreliability. The efficiency band also differs across the ranges of existing power sources thus the need to invent solutions is highly desirable. 2.1.2 Dynamics of Wind Energy In order to calculate the amount of wind power resulting from a given wind turbine the equation (1) below is utilised. (1) Where is the air density at any given time, is the amount of area that is to be swept by the turbine blades, while is the amount of wind blowing across the turbine blades in . Furthermore it is not possible to ensure that all the wind power blowing across the blades is collected and therefore a certain level of percentage efficiency shall be executed at any given point. The air masses behind the turbine action is meant to meet the incoming wind energy as in order to meet a certain theoretical figure which is optimized for every installed wind turbine (Manwell, McGowan, & Rogers, 2009). According to Manwell et al. (2009), Betz was able to discover the maximum speed limit utilizable by a wind turbine back in 1926. The optimum maximized wind speed of a turbine is usually 59% for every rotation. Other mechanical losses that can be observed in a kinetic energy system can too be observed in a wind turbine couple by such losses as electrical losses. The two turbine systems that can be used to illustrate these situations for better understanding include fixed and variable speed systems. For the fixed speed systems, the generator is placed in squirrel type cage that produces energy through induction process. This system runs at a constant speed and therefore gives small variations in comparison too variable speed systems. This characteristic is very important when it comes to direct connection to the grid as the maximum speed variations that do exist from these turbines range between 1 – 2%. This systems are however expensive and cannot be therefore employed in large scale production of wind power (Manwell, McGowan, & Rogers, 2009). The variable speed system on the other side is hard to implement when it comes to grid connections thus it has to be decoupled from the grid. The electronic converter that is usually utilized for such purposes is usually dynamic in terms of the velocity ranges that it can be operated within. The variable speed systems operate at frequencies other than those on the main grid system making it difficult for them to be operated directly (Nielsen, 2010). This thesis therefore looks into the issue of power stabilization due to existence of such power systems by use of SMES for direct synthesis or grid usage. Power turbines are dependent on the wind blowing across their respective systems as can be observed in equation 1 above. Therefore, the cut-in speed and the rated wind power speeds must be indicated for the analysis purpose of any given wind turbine. This usually ranges between for the rated speed while it may range between for the cut-in speed. In event that wind speed for the rated power surpasses the output level as per the manufacturer ratings then the blades are said to be abnormally pitched. This makes wind one of the most unexploited forms of energy especially when the turbine’s predictability has more to measure. Most turbines have a cut-off mechanism that stops them not to exceed a given speed limit of up to. On the other side, it is important to note that wind power can be controlled from any kind of variations when it comes to actuating for purposes of power output (Manwell, McGowan, & Rogers, 2009). The wind speed variation will also vary the output of wind turbines by imparting properties that are likely to differ the frequencies from time to time. These variations are usually caused by such properties of wind such as the diurnal variations which are brought about by change in weather patterns and other long term effects of wind. Although some of these variations can be correctly be predicted so as to avoid short term fluctuations, it is still not practical to connect such power systems to the grid. The variations that may be faced from any wind farm interconnected outputs shall automatically vary with the number of turbines present. The aggregation exercise that is carried out on wind turbines within wind farms also tries to damp away the fluctuations. These fluctuations are due to the fact that the wind gusts cannot hit the same blade points for all the wind turbines present in a wind farm. This means that the wind turbines shall usually experience a deviation of up to 2.5% depending on the quality of the wind at any given time of the year (Manwell, McGowan, & Rogers, 2009). Where distributed generation system is utilised, the power output fluctuations differ from one turbine to the other thereby resulting to severity when it comes to single turbine operation. Fast fluctuation systems may only be countered by utilising systems that may store and release the energy at a given rating. SMES are chosen because they can deliver such high amounts of energy within a given time limit therefore covering the power fluctuations that may be seen from time to time (Nielsen, 2010). 2.2 Superconducting Magnetic Energy Storage 2.2.1 Operating Principles of SMES When energy is stored in an ohmic conductor, it fades out quickly once it is deprived of any further power supply. In order for an SMES to work as an energy storage system, the ohmic characteristics have to be eliminated by all means necessary. In order to eliminate these characteristics, the conductors are induced to extremely low temperatures referred to as cryogenic. This makes the respective conductors to transform into superconductors whose state of resistance normally drops to absolute zero (Bray, 2009). This state defines continuous flow of current for infinite time where in equation (2) below tends to zero while goes to infinity. (2) For a superconductor to maintain its characteristics, the temperatures have to be maintained at a critical range below which the critical current remains at and the magnetic field maintains at. This is however given a safety margin within which these systems can operate. The superconductivity of a material does not necessarily have to be in the cryogenic range. Therefore, these superconductors are divided into high temperature superconductors (HTS) and low temperature superconductors (LTS). The high temperature superconductors are brought down to the cryogenic temperature through use of liquid nitrogen (N). On the other hand, low temperature superconductors are imposed against helium (He) in order to bring them to temperatures ranges of. These technologies are associated to various advantages and drawbacks which include the cost of cooling. For example cooling the conductors utilising liquid nitrogen is very cheap as compared to helium. While higher temperatures of operation makes the conductor brittle to an extent that it cannot be shaped makes it disadvantageous for high temperature superconductors. Low temperature superconductors due to their high system efficiencies also come at a higher price. The low temperature superconductor mostly used is an alloy referred to Niobium-Titanium whose superconducting capabilities optimise at a temperature below (Bray, 2009). Compared to other energy storage systems, the reliability of low temperature superconductors as forms of SMES drops considerably due to the system requirements. It is however notable that the life cycle of the coil itself is considerably long if it were to be compared to the other kind of storage systems in question. SMES efficiency is rated at 90% which is a lot higher in comparison to its counterparts like batteries which however require that the energy be changed from one for to the other i.e. electrical to chemical. Large scale designs for SMES require large sized coils to be designed for reasons related to diurnal compensation of power. This therefore calls the amount of coils to be increased in case the diurnal effects are more prominent in a given area in order to compensate for the losses. The property associated with high energy delivery within a short period of time poses as one of the advantages that is also highlighted in the introduction section (Nielsen, 2010). 2.2.2 Application of SMES in Wind Energy Improvement 2.2.2.1 Improvement of Power Stability Power stability can be mainly improved by decreasing of frequency fluctuations and protecting the grid from critical loads that are most likely to occur during the peak. In enhancing wind energy for grid supply purposes, the SMES systems are very important owing to their ability to convert AC current to DC current among other useful capabilities. However this paper dwells on the magnificent abilities of the SMES to improve the stability and quality of wind power. In adding these desirable features to wind energy, it is evident that most of the wind energy sources are distorted in terms of resulting voltage frequency and current. To enhance the stability of wind energy, SMES actively reduce the low frequency oscillations which are normally in the order of. During power transfers, transmission capacity actively damps these oscillations through real and reactive power modulation systems. Dynamics of voltage power stabilization utilise the insufficient dynamic power in order to maintain given system voltages (Yuan, 2011). Apart from this methodology of reducing the oscillations that are observed in emanating wind power, the fuzzy control strategy has also been applied in the SMES technology in order to come up with transient stability within the system. This methodology poses a lot of advantages towards the elimination of significant frequency fluctuations as it offers synchronous elimination of undesired frequencies. While various strategies have been utilised in system stabilisation, effective control options that seek to achieve optimal control apply artificial intelligence monitoring for full time rectification purposes. In electrical terms this specific AI technology is referred as forward neural network method (Ali, Murat, & Tamura, 2007). Protection against critical loads is also another approach to wind energy stability improvement as this forms of fluctuations are common. The SMES approach towards critical load application is done through smoothing out of the extreme loads which may have a diverse effect on the grid system. Power conditioning is continuously offered by this technology through hysteresis control and regulation of the discharge period in order to eliminate short term disturbances. Connecting efficient protection mechanisms with a higher storage capacity across the grid shall also reduce the critical load encounters thus extending the support time (Aware & Sutanto, 2004). In order to reduce the power fluctuations observed in wind power, the quick response through which the SMES react give a leeway for short term power absorption in order to smoothen the output. This is mainly done by suppressing the oscillations in an integral/ proportional derivative (PID) sequence that seeks to adjust active and reactive power to give a desired output. The configuration of the wind turbine parts does not therefore matter when it comes to delivery of the final product and manufacturers are saved of this worry. The PID controller can also be improved in cases where the tie-line active power id adjusted for bi-directional power conversion. This is to increase the active power resulting from the generation mechanism of the wind turbine. On the other hand, applying the fuzzy control logic in SMES improves stability of the induction generator that is usually connected to the grid. The validity of power conditioning systems therefore possesses a major effect on the SMES as applying intelligent systems will definitely increase the efficiency of power being supplied to the end user. Neural network control has a high efficiency of power stabilization thereby acting as a smart power monitoring system (Ali, Murat, & Tamura, 2007). 2.2.2.2 Improvement of Power Quality Power quality improvement is also covered in SMES due to the introduction of flexible AC transmission systems also referred as FACTS. These forms of inverters usually increase real power as compared to reactive power thereby presenting the system with power improvement benefits. A static synchronous compensator (StatCom) is used to absorb or inject reactive power in order to limit the degree of freedom that can be sustained by the grid. SMES can also be utilised in spinning the reserved balancing asymmetric while decreasing area control errors. When it come to power improvement using SMES systems, the number of coils that are desirable for such a process are usually enormous and can store a huge amount of power (Yuan, 2011). Using the fuzzy-Logic power control strategy, the outcome can be equally levelled in order to give a smooth output. Load fluctuations at the end user may be effectively eliminated through voltage reductions or high load eliminations for which SMES are designed. SMES can be effectively used to compensate for fluctuating outputs through deployment of high intensity synchrotron which can absorb active and reactive power during charging and discharging process. This is usually controlled by an intelligent control mechanism which choses on the actions to be undertaken in way of synchronization (Ise, et al., 2003). Another useful approach utilised by SMES in improving the quality of power is the ability to act as backup power supply mechanism. Where wind farms act as secondary power, the SMES store energy for later release when need arises. Therefore, the magnetic coil size differs from one use to the other in accordance to the amount of power that may be required for a given utility. Utilising this technology gives significant results in terms of power improvement in that when there is insufficient wind power to generate electric current, the SMES may be used for quite a while thereby reducing the risk of losses that power consumers face from time to time (Ise, et al., 2003). 3 Research Methodology The suggested research methodology for this study is mainly through simulation studies owing to the expenses involved in equipment purchase and real life experimentation. The software that shall be utilised for this purpose shall be MATLAB/ SIMULINK which are closely interrelated and compatible. The research objectives shall therefore be modelled in accordance to their descriptions in a bid to demystify their characteristics as if they were acting in real life. The wind turbine shall however be eliminated from the layout and substituted with a probable input to be analysed using SimPower and Fuzzy logic. Extensive research shall be conducted in existing literature to act as a guide and also to offer alternative information from previously carried out researches. The system to be analysed in MATLAB/ SIMULINK is shown in figure 2 below. Figure 3: Power system to be analysed. 3.1 Modelling for Objective 1 The first objective of this research is to demonstrate how SMES can be utilised in resolving the power instability issues associated with voltage fluctuation. In order to model for this objective, the effects of voltage fluctuations shall be applied at the input in order to demonstrate the improvements that can be inferred on resulting output in such a circumstance where there is a variation in wind energy from time to time. The results to be obtained shall then be analysed in order to bring forth the effects pf using the SMES unit as a voltage stabilizer. For the sake of illustration the graphs below were preliminarily obtained so as to indicate the viability of this objective. The graph 1 below was obtained for voltage sag introduced when amidst the power generation process. It can be observed how the SMES reduced the condition thereby reaching the normal condition very fast. Graph 1: Introducing voltage sag as a form of voltage instability. 3.2 Modelling for Objective 2 The second objective looks into demonstrating how SMES can be deployed in resolving the power instability issues related to frequency fluctuations. The frequency fluctuations usually occur as a result of system transients. Fluctuations in these frequencies are addressed for the purpose of stabilizing power through a process called damping. For a test carried out prior to the study, the voltage stability was sought for up to 4 seconds, the following graphs are obtainable when SMES are used in rectifying the frequencies of input voltages from variable wind turbines. It is notable that there is gradual improvement from the input to the output. Graph 2: SMES stabilization of input voltage frequency. 3.3 Modelling for Objective 3 kIn order to demonstrate how wind power quality can be enhanced using flexible AC transmission systems (FACTS) approach. The current voltage control mechanisms usually control voltage source by injecting harmonic phases effectively. The improvement in power quality depends on the induction generator although in this circumstance the capacitor batteries are used to explain the effectiveness of SMES through a comparative approach. Therefore the simulation takes the same approach although the SMES is substituted with a capacitor for load variation indication. The dynamism achieved when this exercise is carried out in a single second is magnificent as the FACTS system can regulate single system energy. Therefore, the research shall be looking into its usage for other purposes such as single turbinepower improvement. The graphs below shall be obtained in case of the simulation exercise to offer a comparative approach to the problem at hand. Graph 3: Wind induced voltage. Graph 4: Resulting voltage following FACTS improvement. 4 References Ali, M. H., Murat, T., & Tamura, J. (2007). Superconducting Magnetic Energy Storage for Transient Stability Augmentation. IEEE Transactions on Control Systems Technology, pp 144-150. Aware, M., & Sutanto, D. (2004). SMES for Protection of Distributed Critical Loads. IEEE Transactions on Power Delivery, pp 1267-1275. Baggini, A. (2008). Handbook of Power Quality. Chichester, West Sussex: John Wiley & Sons. Beguin, F., & Frackowiak, E. (2009). Carbons for Electrochemical Energy Storage and Conversion Systems. Broken Sound Parkway NW: CRC Press. Bray, J. (2009). Superconductors in applications; some practical aspects. Applied Superconductivity, pp 2533–2539. Chen, L., Liu, Y., Arsoy, A., Ribeiro, P. F., Steurer, M., & Iravani, M. R. (2006). Detailed modeling of superconducting magnetic energy storage (SMES) system. Power Delivery, IEEE Transactions, pp.699-710. Denholm, P., Ela, E., Kirby, B., & Milligan, M. (2010). The Role of Energy Storage with Renewable Electricity Generation . Cole Boulevard, Golden, Colorado: National Renewable Energy Laboratory. Ise, T., Furukawa, K., Kobayashi, Y., Kumagai, S., Sato, H., & Shintomi, T. (2003). Magnet Power Supply with Power Fluctuation Compensating Function using SMES for High Intensity Synchrotron. IEEE Transactions on Applied Superconductivity, pp 1814-1817. Joint Implementation Network. (2014). Energy Storage: Superconducting magnetic energy storage (SMES). Retrieved October 06, 2014, from Climate Tech Wiki: http://www.climatetechwiki.org/technology/jiqweb-ee Manwell, J. F., McGowan, J. G., & Rogers, A. L. (2009). Wind Energy Explained: Theory, Design and Application. Chichester, West Sussex: John Wiley & Sons. Nielsen, K. E. (2010). Superconducting magnetic energy storage in power systems with renewable energy sources. Norwegian University of Science and Technology. Office of Energy Efficiency & Renewable Energy. (2014, October 4). History of Wind Energy. Retrieved from Energy.gov: http://energy.gov/eere/wind/history-wind-energy Pahlavani , M. A. (2011). Compensation of Reactive Power and Sag Voltage Using Superconducting Magnetic Energy Storage System, Power Quality Monitoring Analysis and Enhancement. Rijeka, Croatia : Intech Open Science. Runyon, J. (2014, October 6). GWEC: Global Installed Wind Power Capacity Will (Almost) Double in Five Years. Retrieved from http://www.renewableenergyworld.com/rea/news/article/2014/04/global-wind-market-is-just-fine-thank-you Salih, E. (2012). Application of Superconducting Magnetic Energy Storage unit for Improvement of Stability and Quality of Power Systems. Joondalup, WA: Edith Cowan UIniversity. Whittingham, M. S. (2012). History, Evolution, and Future Status of Energy Storage. Proceedings of the IEEE, pp 1518-1534. Yuan, W. (2011). Second-Generation High-Temperature Superconducting Coils and Their Applications for Energy Storage. New York: Springer Science & Business Media. 5 Appendix 5.1 SMES Controller Model function [x, y, z] = fcn(I1, I2, Ir) %#codegen %charging %U = 100 %L = 0.2 %Re = 5 %I0 = 10 %A = -Re/L %B = U/Re %t= [0:0.05:0.1;0.15:0.05:0.25;0.3:0.05:0.4] %C=t*A %I = [] %I={I0*expm(C)}+B*{1-expm(C)} %I=10*expm(t*A)+20*(1-expm(t*A)) %tspan=[0,1,2,3] %t=tspan %I(t)= 10*2.56^(t*A)+20*(1-2.56^(t*A)) if I1>I2 X=I1,y=I1,z=I1; end %storing if I1=I2 X=0,y=0,z=I1; end %discharging if I1I1 X=0,y=0,z=I1; end y = u; Read More